G proteins of the G12 family are activated via thromboxane A2 and thrombin receptors in human platelets

Stefan Offermanns, Karl Ludwig Laugwitz, Karsten Spicher, Günter Schultz

Research output: Contribution to journalArticlepeer-review

409 Scopus citations

Abstract

Using subtype-specific antisera, we were able to identify the recently described α subunits of G12 and G13 in platelet membranes as 43-kDa proteins. Activation of the thromboxane A2 and the thrombin receptors in platelet membranes led to increased incorporation of the photoreactive GTP analogue [α-32P]GTP azidoanilide into immunoprecipitated α12 and α13, indicating that both receptors couple to G12 and G13. In addition, both activated receptors were demonstrated to couple to one or more members of the Gq family. In the absence of receptor agonists, incorporation of [α-32P]GTP azidoanilide into α12 and α13 was low over a long time period (up to 45 min) due to an obviously low basal nucleotide exchange rate, whereas an agonist-stimulated photolabeling of α12 and α13 could be observed after 4-8 min and reached a maximum after 30-45 min. Effective activation of G12 and G13 via the thromboxane A2 and the thrombin receptors was not dependent on the presence of GDP. Our results provide evidence that G12 and G13 play a functional role in transmembrane signal transduction and suggest that both proteins are involved in pathways leading to platelet activation.

Original languageEnglish
Pages (from-to)504-508
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Volume91
Issue number2
DOIs
StatePublished - 18 Jan 1994
Externally publishedYes

Keywords

  • Signal transduction

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